Pipelines or pipe networks for transmission and supply of gaseous fuels, such as town gas or natural gas, are often built underground. They are vulnerable to ingress of water in the case of accidents (e.g. leakage caused by nearby underground work and in particular damage by impinging water jets from burst water mains) or unexpected circumstances (e.g. soil/earth movement, and cracking or faulty condition of pipe fittings). Underground water leaking into the system may find its way spreading very quickly over a long distance down the pipeline. Such water will take considerable time to clear, subsequent to rectification of the leak or faulty condition. To worsen the problems, water carrying soil or dirt, etc. may reach and foul or cause damage to gas equipment/apparatus at the customers' premises.
As present, measures safeguarding or catering for the ingress of water into underground pipelines are rare or impractical.
The invention seeks to eliminate or at least to mitigate such a problem by providing a new or otherwise improved shut-off device for pipe for use in a pipeline for operation in response to ingress of water.